McLEOD, CARVER COUNTIES, MN  From traffic volume to accident counts, not all of Highway 7’s crossroads are created equal.

“There are four main types of intersections  two-way stops, all-way stops, signal lights, and roundabouts,” said Minnesota Department of Transportation (MnDOT) engineer Paul Kachelmyer. “Each one of these has pluses and minuses to it.”

Kachelmyer was the project engineer for two roundabouts along Highway 7 that were installed midway through 2008. One is at Carver County Road 10, and the other is at Highway 25, north of Mayer.

For those two intersections, roundabouts were deemed the best traffic control choice to reduce accidents.

“What was happening there were bad right angle crashes,” Kachelmyer said. “Cars going across Highway 7 would pull out in front of cars going 60 miles per hour.”

According to national statistics, there is a 90 percent reduction of serious injury accidents after a roundabout is installed, and a 60 to 70 percent reduction in overall accidents.

“They have ratings for every road, and intersections in the state are ranked from worst to best,” Lownsbury said.

“We look at what the circumstances are, and what potential solution might help,” Kachelmyer added.

Traffic volumeTraffic volume data is calculated every few years, according to Lownsbury.

“We put out mechanical traffic counters at different locations, and leave them there for 24 to 48 hours,” he said.

About 3,300 vehicles are on Carver County Road 25 near Highway 7 per day, according to MnDOT data. On Highway 7, between 7,800 to 8,800 vehicles travel near that intersection daily.

The traffic increases to the east, with 3,850 to 4,500 vehicles intersecting at Carver County Road 10, and 8,800 to 10,200 along Highway 7 per day.

Farther from the Twin Cities, traffic tends to decrease.

Along McLeod County Road 9, there are 930 to 1,600 vehicles passing through each day, with about 6,900 on Highway 7 near that intersection.

Traffic picks up slightly at the intersection of McLeod County Road 1, which goes from Winsted to Lester Prairie. Daily, about 2,700 to 4,400 vehicles travel along McLeod County Road 1, and 6,800 vehicles travel in that area on Highway 7.

Traffic lightsWhen an intersection is especially congested, traffic lights are often utilized.

“A lot of people don’t know that the purpose of a traffic light is to regulate traffic flow,” Kachelmyer said. “Most people would think it’s safer, but accident rates usually go up when signal lights are put in.”

However, severe accidents are often reduced, he added.

One example is on Highway 36 near Stillwater, where a traffic light was installed seven years ago. After the light was added, accidents were up by 70 percent, but the number of people seriously injured was cut in half.

“The traffic volume was way too high to make a roundabout reasonable,” Kachelmyer said.

The criteria for installing a roundabout or traffic light is not narrowly defined.

“It’s very much a case-by-case basis,” Kachelmyer said. “It’s a judgment call.”